- 1,4,2-Diazaphospholidine-3,5-diones and related compounds: A lecture on unpredictability in catalysis
-
1,4,2-diazaphospholidine-3,5-diones and related compounds and unpredictability in catalysis was studied. The five-membered ring species 4 6, which are all readily accessible by the McCormack reaction, optionally with subsequent hydrogenation, were selected for this study. The use of saturated species of type 4 (1-organyl-phospholanes) as catalysts led to a complete reverse in the selectivity of the reaction, in favor of the formation of the isocyanate trimers. Owing to the high activity of the corresponding P-oxides in carbodiimidization reactions, it can be assumed that the findings can be attributed to partial air oxidation of the trivalent phosphorus species applied. The symmetrical species 6, in total contrast to the other two members of the series, do not exhibit any catalytic activity with respect to isocyanates and instead react cleanly with two equivalents of isocyanate to effect the extrusion of 1,3-diene.
- Richter, Frank U.
-
supporting information; experimental part
p. 5200 - 5202
(2009/12/24)
-
- Process for making dialkyl carbonates
-
A process for the production of dialkyl carbonates from the reaction of alcohol, for example C1-C3 alcohols, with urea is disclosed wherein the water and ammonium carbamates impurities in the feed are removed in a prereactor. The water is reacted with urea in the feed to produce ammonium carbamate which is decomposed along with the ammonium carbamates originally in the feed to ammonia and carbon dioxide. In addition some of the urea is reacted with the alcohol in the first reactor to produce alkyl carbamate which is a precursor to dialkyl carbonate. Dialkyl carbonates are produced in the second reaction zone. The undesired by-product N-alkyl alkyl carbamates are continuously distilled off from the second reaction zone along with ammonia, alcohol and dialkyl carbonates under the steady state reactor operation. N-alkyl alkyl carbamates can be converted to heterocyclic compounds in a third reaction zone to remove as solids from the system.
- -
-
Page/Page column 8; 9
(2008/06/13)
-
- A new simple synthesis of 3,5-disubstituted 1-amino-1,3,5-triazine- 2,4,6-triones from ethoxycarbonylhydrazones and isocyanates
-
The 3,5-disubstituted 1-amino-1,3,5,-triazine-2,4,6-triones were synthesized in good yields from aromatic aldehyde or ketone ethoxycarbonylhydrazones by treatment with aryl or methyl isocyanates in boiling triethylamine followed by hydrolysis with hydrochloric acid solution.
- Chau,Malanda,Milcent
-
p. 261 - 263
(2007/10/03)
-
- Studies of Reactions of 1,3,5-Trimethylbiuret and 1,3-Dimethylurea with Chloroform
-
1,3,5-Trimethylbiuret and 1,3-dimethylurea react with chloroform at temperatures above 200 deg C to produce 1,3,5-trimethyl-1,3,5-triazinane-2,4-dione (4), 1,3-dimethyl-1,3,5-triazinane-2,4,6-trione (5), and 1,3,5-trimethyl-1,3,5-triazinane-2,4,6-trione (3), besides minor quantities of other by-products, via trimerization reactions involving MIC, isocyanic acid, and N-methylenemethylamine.
- D'Silva, Themistocles D. J.,Lopes, Anibal
-
p. 795 - 796
(2007/10/02)
-
- Studies of Methyl Isocyanate Chemistry in the Bhopal Incident
-
Following the methyl isocyanate leak from Tank 610 at the Bhopal plant, the residual material from the tank was analyzed for its contents.Approximately 70percent of the residue was comprised of three cyclic materials: 1,3,5-trimethyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione or methyl isocyanate trimer (5), 1,3-dimethyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione or dimethyl isocyanurate (6), and dihydro-1,3,5-trimethyl-1,3,5-triazine-2,4-(1H,3H)-dione or dihydrotrimethyltriazinedione (7).Minor quantities of methyl-substituted ureas, biurets, and amine hydrochlorides were also found.The composition of the residue was replicated very closely by the products obtained when a mixture of methyl isocyanate (84.4percent), chloroform (12.0percent), and water (3.6percent) was heated at 225 deg C under pressure in a stainless steel reactor.Experimental results are consistent with the view that under these conditions methyl isocyanate reacts initially with water to form 1,3-dimethylurea (1) and 1,3,5-trimethylbiuret (2).At temperatures between 100 deg C and 225 deg C these products decompose to reactive intermediates which further react exothermically to form the aforementioned cyclic materials, trimethylurea, and mono-, di-, and trimethylamine hydrochlorides.The decomposition of 1 and 2 is facilitated by the presence of chloroform and metals.Other experiments involving 13C-enriched chloroform have given support to the proposed mechanisms for formation of 6 and 7.
- D'Silva, Themistocles D. J.,Lopes, Anibal,Jones, Russell L.,Singhawangcha, Sureerat,Chan, John K.
-
p. 3781 - 3788
(2007/10/02)
-